Horticulture Principles and Practices

REFERENCES AND SUGGESTED

REFERENCES AND SUGGESTED READING Copeland, L. O. 1976. Principles of seed science and technology. Minneapolis: Burgess. Hartmann, H. T., and D. E. Kester. 1983. Plant propagation: Principlesand practices, 4th ed. Englewood Cliffs, N.J.: Prentice Hall. Mayer, A. M., and A. Poliakoff-Mayber. 1975. The germination of seeds, 2d ed. Oxford: Pergamon Press. Sexual reproduction in angiosperms http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Angiosperm.html Stefferud, A., ed. 1961. Seeds: USDA yearbook of agriculture. Washington, D.C.: U.S. Department of Agriculture. PRACTICAL EXPERIENCE 1. Plant seeds of a legume and a grass in a soilless medium. a. Observe the pattern of germination between the two plant types. b. Wash away the potting medium and compare the anatomical differences between the legume and the grass. 2. Test the germination percentage of a seed a. Purchased from various sources (e.g., grocery, nursery, and supermarket) b. Produced in different seasons (1, 2, 3 years) c. Stored under different conditions (e.g., cold storage, freezer, and room temperature) OUTCOMES ASSESSMENT 1. Distinguish breeder seed and certified seed. 2. What is seed law and why is it important in the seed industry? 3. Describe, giving examples, the techniques growers may use to enhance the germination capacity of seeds. 4. Discuss the importance of seed analysis to horticultural crop production. 5. Discuss how seed emergence and seed size are considered in crop production. 6. What is hardening off and what is its importance in crop production? 7. Give the major purposes of plant propagation. Outcomes Assessment 311

10 Asexual Propagation PURPOSE AND EXPECTED OUTCOMES This chapter discusses the methods of propagating horticultural plants by using materials other than seed. After studying this chapter, the student should be able to 1. Distinguish between sexual and asexual methods of propagation. 2. Discuss the advantages and disadvantages of asexual propagation. 3. Describe propagation by cutting. 4. Describe propagation by budding. 5. Describe propagation by grafting. 6. Describe propagation by layering. 7. Describe propagation by underground plant parts. 8. Describe and discuss micropropagation. [COLOR PLATES—see color plate 7 for additional chapter photos] Clone An individual or a group of individuals that develop asexually from cells or tissues of a single parent individual. 312 OVERVIEW When plants are propagated by any material other than seed, they are said to be asexually, or vegetatively, propagated. Since the sexual mode of reproduction is the principal means by which biological variation is generated (through recombination), propagation that circumvents the sexual mechanism (asexual, or vegetative, propagation) results in no genetic changes. The progeny, or offspring, are genetically identical (clones). Therefore, instead of meiosis, mitosis is the mechanism governing asexual propagation. Species that are heterozygous and hence fail to reproduce true to type may be propagated vegetatively or clonally to preserve the genotype. Trees or woody perennials benefit from this method of propagation, since it drastically shortens the time of breeding of such plants. The vegetative tissues commonly used in asexual propagation are the stem, leaf, and root. Modern technology allows full-fledged plants to be regenerated from tissues and even single cells (micropropagation). A common phenomenon that occurs in some